The challenge for remotely monitored alarm systems has always been to ensure that the automatic alarm announcement resulting from an alarm condition is correctly received at the monitoring site, being a security company or the like, or in some instances, the alarm can be announced to local security authorities such as the police.
At their most basic form, burglar alarm systems provide an automatic telephone calling system over the normal wired telephone land line service to announce alarm conditions at a monitored site.
This system has a number of inherent disadvantages in that,    1) A burglar can cut the land line and subsequently deactivate the alarm system and thereby gain entry to premises without being detected    2) Faults in the telephone network may prevent the announcement from being received at the monitoring site    3) At the time the burglar alarm system uses the telephone land line to make an automated announcement the telephone land line is not available for others to make, say an emergency telephone call    4) As burglar alarm systems can not be uniquely identified by their own address (see U.S. Pat. No. 6,381,307 Sur-Gard Security Systems Ltd) it is a simple matter to have an unauthorised burglar system masquerading as the authorised one thereby defeating the security system
In another known system (see U.S. Pat. No. 5,131,019, VerSuS Technology, Inc.), it has been proposed to additionally provide a cellular telephone or like radio communication device which can be activated to announce a burglar entry to the premises protected by the alarm if the telephone land line is cut.
This system has a number of inherent disadvantages in that,
    1) Faults in the telephone network may prevent the announcement from being received at the monitoring site    2) An announcement is only sent to the monitoring site infrequently allowing the system to be disabled unbeknown to the security company, for example by a disgruntled employee    3) As burglar alarm systems can not be uniquely identified by their own address (see U.S. Pat. No. 6,381,307 Sur-Gard Security Systems Ltd) it is a simple matter to have an unauthorised burglar system masquerading as the authorised one thereby defeating the security system
In another known system (derived channel monitoring system, see U.S. Pat. No. 4,442,320, Base Ten Systems, Inc.), it has been proposed to monitor the remote alarm system and the telephone land line from the telephone company's local exchange using specialised equipment installed and operated by the telephone company that directs alarm announcements to security companies or the like, or in some instances, to local security authorities such as the police. This system thus has a need for specific alarm carriage equipment in the telecommunications network which is used to collate the alarm information for retransmission to the monitoring station.
Such an Alarm Monitoring System is shown in FIG. 1 and comprises specialised alarm equipment at the remote site or customer premises, alarm scanning equipment at the local telephone exchange, central station equipment located at one of the telephone company's offices and specialised equipment at the security company. One implementation of this type of system is given below,    1) The burglar alarm system or associated equipment is connected to the telephone land line and generates a low frequency out of band signal (low tone) that is received at the telephone company's local exchange    2) The Alarm Scanning Equipment located at the telephone company's local exchange regularly polls the burglar alarm system or associated equipment with voice frequency modem signals over the telephone land line    3) The absence of low frequency signal (low tone) from the burglar alarm system or associated equipment results in the alarm scanning equipment located at the telephone company's local exchange sending a poll request to the burglar alarm system or associated equipment    4) The burglar alarm system or associated equipment responds to the poll from the alarm scanning equipment located at the telephone company's local exchange by sending as part of the poll response message the identification of the outstanding alarms. The message is forwarded to the telephone company's Central Station equipment where it is converted into an alarm announcement message which is sent to the security company over the telephone company's data network.    5) In the event that the alarm Scanning equipment located at the telephone company's local exchange does not get a response to a predetermined number of poll request messages, it informs the Central Station equipment which generates an alarm announcement message indicating that the monitored site is no longer accessible for the purposes of remote monitoring. This message is sent to the security company over the telephone company's data network.
This system has a number of inherent disadvantages in that,    1) It can only be used where the telephone company has deployed the Central Station equipment and then only from specific telephone exchanges where connection to the Alarm Scanning equipment is available    2) Redundant paths from the burglar alarm system are not supported. A failure of the Alarm Monitoring system prevents the burglar alarm system from sending any announcements to the security company.    3) The polling process uses voice frequency signalling that interferes with the use of data modems and faxes on the telephone land line    4) The low frequency out of band signal (low tone) generated by the burglar alarm system or associated equipment is incompatible with telecommunications equipment commonly used in the customer access network (last mile), further limiting the application of this technology    5) The signals transmitted on the analogue link may be encrypted, although in practice any such encryption may be detected and broken over relatively short time scales. Once the code has been broken, then an attack may be made by cutting into the line and substituting a dummy terminal which masquerades as the real terminal. This makes it possible to disable the security system at the customer premises without the monitoring service being alerted.    6) The burglar alarm system or associated equipment used for this system implement proprietary signalling and are therefore more expensive than standard burglar alarm systems that provide an automatic telephone calling system over the normal wired telephone land line service to announce alarm conditions at a monitored site    7) This system and other similar digital embodiments require the use of intermediate equipment (Central Station in FIG. 1) often controlled by a third party for example the telephone company which manipulates and relays the alarm messages to the security company    8) In this system the alarm equipment sends an announcement only when polled by the intermediate equipment (Central Station in FIG. 1)    9) The message transfer time of this system is determined by the polling rate set by Alarm Scanning equipment
In another known system (ISDN monitoring system, U.S. Pat. No. 6,377,589, British Telecommunications public limited company), it has been proposed to monitor the alarm system and the telephone land line from the telephone company's local exchange by providing the telephone service over an ISDN basic rate access system over the land line.
Such a system is shown in FIG. 2 and comprises specialised alarm equipment at the remote site or customer premises, ISDN Terminal Adaptor equipment, ISDN NT1 equipment, Central Station equipment located at one of the telephone company's offices and specialised equipment at the security company. One implementation of this type of system is given below,    1) The Central Station equipment located at one of the telephone company's offices sends regular poll request messages to the burglar alarm system or associated equipment over the ISDN ‘D’ channel    2) The burglar alarm system or associated equipment responds to the poll request messages over the ISDN ‘D’ channel and in the same message sends any pending alarm announcements to the Central Station    3) The Central Station forwards the alarm announcements to the security company over the telephone company's data network    4) Redundancy is supported over the GSM network with SMS (Short Message Service) text messages
This system has a number of inherent disadvantages in that,    1) It can only be used where the telephone company has deployed the Central Station equipment    2) SMS text messages do not have guaranteed delivery times and do not represent a reliable form of back-up. (Fire alarms are required to report within 15 seconds).    3) The burglar alarm system or associated equipment used for this system implement proprietary signalling and are therefore more expensive than standard burglar alarm systems that provide an automatic telephone calling system over the normal wired telephone land line service to announce alarm conditions at a monitored site    4) To use this system the users must replace their existing telephone system with an ISDN based system potentially incurring significant cost and the inconvenience of having a new telephone number assigned    5) This system and other similar digital embodiments require the use of intermediate equipment (Central Station in FIG. 2) often controlled by a third party for example the telephone company which manipulates and relays the alarm messages to the security company    6) In this system the alarm equipment sends an announcement only when polled by the intermediate equipment (Central Station in FIG. 2)    7) The message transfer time of this system is determined by the polling rate, furthermore, multiple poll periods are required to identify a break in the land line making this system unsuitable in some critical applications where the line break condition needs to be rapidly identified
Another known system has set out to use the instant messaging capability of wide area networks, and in particular the Internet for the carriage of alarms. Patent application WO 01/11586 A1 describes such a system which uses a computer located in the customer premises to collect alarm indication from sensors connected to it, and uses the Internet and a central web site to report alarms and heart beat messages. The central web site reports to a response provider that either an alarm has occurred in the customer premises or that the computer in the customer premises is unreachable.
This system has a number of inherent disadvantages in that,    1) It uses the public Internet which is significantly less secure than a private data network    2) It uses a central web server which is exposed to the known denial of service attacks that can disable the entire security system leaving the customer premises unprotected    3) The computer in the customer premises which is in communication with the central web site is also used to directly acquire alarm sensor data thereby forcing the customer or user of the system to replace their existing alarm system    4) The system does not provide a fall back path to be used in the event that the connection to the Internet has been lost
U.S. Pat. No. 5,943,394 (Detection Systems Inc.) describes an alarm interface system including a dialler intercept unit which connects both to the PSTN and a wide area computer network. This system connects to standard alarm systems and automatically selects, based on pretermined signals from the alarm system whether the signal is sent as is over the PSTN or is translated and sent over the wide area data network.
This system has a number of limitations, including,    1) The system connects to the wide area network through a local area network, such as Ethernet. Ethernet is a shared medium and is well known for not providing a secure link    2) The system is vulnerable to outages of the wide area network resulting from mains failures
In addition, all the systems described above share the limitation that they are not directly suitable for the carriage of video.
Various telemetry and remote premises supervision systems have been proposed that use video cameras to detect motion. When motion is detected via some form of image comparison a remote alarm indication is generated and the automatic recording of video information is triggered. Some of these systems provide remote access to the video data captured to provide visual verification of alarms to eliminate false alarms. One such scheme is described by U.S. Pat. No. 6,271,752 by Lucent Technologies Inc (US).
These systems have a number of inherent disadvantages in that,    1) They operate completely independently of any alarm system currently installed in the customers premises    2) The video information is only recorded from the instant that the alarm condition has been identified, omitting events leading up to the alarm condition    3) The use of motion detection to raise alarms is susceptible to false alarms being reported
The recent introduction of ADSL systems for broadband access has created a problem for burglar alarm systems that provide an automatic telephone calling system over the normal wired telephone land line service to announce alarm conditions at a monitored site. The modem used to terminate the ADSL service at the customer premises generates high frequency voltage signals that interfere with the operation of the automatic telephone calling system of the aforementioned burglar alarm systems, necessitating the installation of specialised signal filters by specialist technicians to eliminate the interference.
It is therefore an object of the present invention to mitigate one or more of the aforementioned problems.
In particular, it is advantageous to provide a system which can be interposed between existing alarm and monitor systems.